Long steep slopes on hills and mountains present a continuing danger that loose rocks or boulders may roll onto roadways or other public areas causing injury to individuals and equipment in the area. These boulders are often dislodged during rainstorms or other inclement weather causing them to roll down the slope at high velocity with the potential of causing severe injury to persons and damage to anything they may hit.
Various attempts to minimize the possibility of the boulders intruding upon roadways and other public areas have been attempted. Rigid fences or barriers have been constructed, but because of the great force created by the boulders as they pick up speed rolling down the hill, they often crash through the rigid fences or barriers and continue their path down the slope.
Attempts have been made to design flexible fence barriers which work in combination with cables to give away when impacted by the boulders. Examples of the developments in this technology are French Patent No. 2,414,586; Swiss Patent No. 656,659; Swiss Patent No. 672,157 and U.S. Pat. No. 4,730,810 to Rambaud. Also, U.S. Pat. No. 4,819,915 to Cargnel discloses a flexible barrier wherein vertical posts are pivotally mounted and normally held in an upright position by means of cables. Upon impact of the barriers with rocks, the posts will pivot, this pivoting motion being resisted by the cables. The fence sections may be provided with cross cables to resist the impact of a rock or other load hitting the fence as shown in German Patent No. 1,459,804.
While each of the foregoing prior art devices is suitable for its intended purpose, the structures are complicated and therefore excessively expensive and have not met with wide scale acceptance. Also, those that have pivotal posts are only good for one time use. That is, once the posts have pivoted over, they stay in that position until they are reset in an upright position and the supporting cables are readjusted to hold them.